cooling
STEPPED BENEFITS
Martin Passingham of Daikin UK explores the unique environment required by server rooms and telecom
shelters, and the benefits of a two-step cooling system design.
U
nlike a standard living
environment such
as a home or office,
infrastructure cooling
requires a constant,
specific set of climatic conditions to
ensure downtime is minimalised. Any
unexpected or planned interruptions
not only incur unplanned business
costs but also impact upon the
service provided to customers, who
rely on consistent access to their
data connections.
Understanding and maintaining
the specific climatic requirements
of a server room or telecom shelter
is essential. In a typical residential
32
or commercial property, humidity
is present and the temperature
control capacity is balanced.
However, in an infrastructure cooling
environment, there is limited or no
humidity due to the vast number
of computers, servers and other
technologies generating minimal
moisture. This is beneficial for the
unique environment as high humidity
can lead to condensation, which
can cause corrosion or, in extreme
circumstances, electrical shorts. On
the other end of the spectrum, too
little humidity can promote a build
up of electrostatic charge that can
destroy sensitive electronics.
Therefore, the relative humidity
(RH) within the centre should be
less than 30 per cent and the
temperature set at 20-22°C. This
then provides the ideal atmospheric
conditions for the computers within
the centre to operate.
When considering installing
an air conditioning system, for
normal cooling applications a
combination of indoor and outdoor
units with matching capacities are
traditionally used. This is due to
the indoor unit having the ability,
and additional cooling capacity,
to withstand the higher humidity
conditions and varying temperature
requirements associated with a
living environment.
Applying this logic to an
infrastructure cooling environment
can, however, have detrimental
consequences, comprising reliability
and resulting in frequent downtimes.
Asymmetric system
Due to the need to extract heat energy
from dry air, the indoor unit needs
enhanced cooling capabilities for
continuous heat transfer. Therefore an
asymmetric system is recommended.
An asymmetric air conditioning
combination pairs a larger capacity
indoor unit with a small outdoor unit,
for example, a 71 class exterior unit
and a 100 class indoor unit. A twostep system design process takes
into account all influencing factors,
as well as back up plans should a
unit fail.
When approaching the system
design, step one determines
the indoor conditions and the
required cooling demand. Step two
then enables a suitable system
combination to be selected from a
unit combination table, providing a
bespoke solution that ensures the
appropriate capacity is available to
meet the indoor cooling demand.
Pairing a larger indoor unit with a
smaller exterior air conditioning unit
presents several unique benefits. For
example, the asymmetric combination
provides a 20-40 per cent increase